Laminated countertops are constructed with a thin surface layer of plastic laminate, such as FORMICA™ brand laminate from the Formica Corporation, Cincinnati, Ohio. The laminate is generally made up of layers of colored paper impregnated with polymeric resin and pressed into sheet stock. For example, a plurality of paper core sheets may be impregnated with a thermosetting phenolic resin and surfaced with a decorative sheet which is impregnated with a noble thermosetting resin. Exemplary laminates are disclosed in U.S. Pat. Nos. 1,956,314; 3,846,217 and 6,551,678. Alternative forms of lamination are known, such as NUVEL™ by the Formica Corporation, as for example described in U.S. Pat. No. 6,110,313.
The surface of a laminated countertop is typically bonded to a wood fibre core, such as plywood, particleboard or flake board. A wide variety of methods, adhesives and machines may be used for attaching the laminate to the core, as for example are disclosed in U.S. Pat. No. 3,668,033. These process include both stationary and continuous processes, and typically involve the application of heat and pressure to affix the laminate to the core.
To mount a sink in a laminated countertop, a cross-sectional hole must be cut through the laminate and core. The wood fibre core exposed by the cross-sectional cut is generally porous, so that a seal must be used to exclude water from the unlaminated, cut edge of the countertop. Typically, this is achieved by dropping a sink with an upper circumferential flange into the mounting aperture from above, and sealing the flange against the laminated countertop.
The traditional mounting for flanged drop-in sink gives rise to a number of problems. Because the flange is raised or beveled, it is not possible to run cleaning solution over it freely, since the cleaner would not run back into the sink but out over the countertop. Perhaps more importantly, if the seal between the sink flange and the countertop laminate deteriorates, water can leak down into the exposed porous wood fibre edge of the countertop core. The positioning of the flange above the wood fibre edge facilitates this undesirable flow. Eventually, the countertop may suffer structural failure as the wetted core first swells, then looses its structural integrity altogether. Even before the fibre core fails, however, the area beneath a leaking sink flange may become an unsanitary habitat for the proliferation of microorganisms.
There are a variety of ways in which a sink may be mounted to the underside of an aperture cut in a laminated countertop, as for example are disclosed in International Patent Publication WO 96/04820 and U.S. Pat. Nos. 5,551,103; 5,754,991; 6,349,429. In some cases, somewhat elaborate manufacturing steps may be employed to effectively undermount a sink in a laminated countertop, as for example described in U.S. Pat. No. 7,007,317.